This invention concerns a sheath for the needle of a hypodermic syringe.
Hypodermic syringe assemblies are usually provided with a protective sheath covering the needle for its protection until the syringe is required for use.
It is a common, though by no means universal, practice to change the needle of a syringe after filling and before administration of the injection because of a perception that the original needle may become blunted, bent or subjected to loss of needle lubricant during the filling operation, for example by insertion through the rubber cap of the vial, contaminated with a foreign substance, for example latex from such a cap or rendered unsterile.
In the case of syringes with provision for retraction of the needle after use as disclosed for instance in our prior EP-A-0776225, the needle assembly tends to be specially designed for this purpose and it is not therefore practical to contemplate changing needles after filling the syringe and before administering the injection.
There are also concerns over the risks of drawing in fragments or slivers of material, e.g. glass, when the syringe is filled from for example an ampoule following breaking of a glass or other cap of the ampoule. Moreover, if the same needle is used to fill the syringe and also administer the medication, some injection fluid may be present on the outside of the needle which may be undesirable since some substances for injection can be irritating to the skin.
These matters are addressed by various aspects of the present invention. The invention has particular, but not necessarily exclusive, application to the type of syringe which incorporates a needle retraction mechanism and is thereby not readily amenable to the possibility of needle change between syringe filling and admistration of the injection.
According to one aspect of the present invention there is provided a hypodermic syringe having a barrel, a hollow fluid dispensing needle which projects from the barrel, means for retracting the needle after use from the projecting position to a retracted, inaccessible position, and a sheath which is removably engageable with the syringe to sheath the needle and provide an interior zone for communication with the internal bore of the needle, the sheath being apertured to admit liquid to said zone whereby liquid drawn through the needle into the syringe first passes into said zone.
The sheath may be shaped or adapted so as to be capable of penetrating the rubber cap of a vial or the like. To this end, it may be provided with a pointed end or a separate needle. In this way, the sheath may be used as a needle during filling of the syringe thereby avoiding any risk of compromising the needle proper as discussed above through having to use the needle proper to pierce a rubber cap for instance.
When used with a syringe having needle retraction means, the needle need only be exposed during the time that it is actually in use for the administration of an injection. At all other times, including filling of the syringe, the needle may be effectively inaccessible thereby considerably reducing the risk of needle stick injuries since the sheath need not be particularly sharp as it is only used for filling the syringe.
It will be appreciated that the sheath is not limited to use with syringes of the type provided with needle-retracting means.
According to a second aspect of the present invention there is provided a sheath which sealably connects over the needle of a hypodermic syringe and is optionally shaped or adapated to penetrate the rubber cap of a vial or the like, the sheath being apertured to allow the ingress of liquid to an interior zone thereof whereby liquid drawn through the needle into the syringe first passes into said zone, filter means being incorporated in the sheath to exclude the entry of particulate material into said zone.
According to a further aspect of the present invention there is provided a sheath which sealably connects over the needle of a hypodermic syringe and is optionally shaped or adapated to penetrate the rubber cap of a vial or the like, the sheath being apertured to allow the ingress of liquid to an interior zone thereof whereby liquid drawn through the needle into the syringe first passes into said zone, needle-wiping means being incorporated in the sheath and arranged so that removal of the sheath automatically wipes the needle to remove any excess liquid on the outside thereof.
The sheath may, if desired, incorporate both filter means and needle-wiping means.
The filter means may be be take take various formsxe2x80x94for example the filter means may be composed of fibrous material or it may comprise a sintered plastics material. Examples of suitable materials include hydrophilic and hydrophobic materials. The plastics materials employed may for instance be selected from the following, including combinations thereof: nylon, polyurethane, polyester, polyolefin, polyethylene, PTFE, acetal, acrylonitrile butadiene styrene and styrene acrylonitrile. Most of these materials can be processed in a number of ways with the exception of PTFE which will generally be sintered. The other materials can be moulded with a foaming agent to give an open cell foam with controllable porosity or made into a non-woven fibrous mat by using a binder compound. Suitable filter materials for use in the present invention are obtainable from for example GVS Srl of Bologna, Italy and Filtertek BV of Limerick, Eire.
The needle-wiping means is conveniently in the form of a thin web or membrane through which the needle extends in use so that when the sheath is removed from the sheath, the marginal edge of the web or membrane surrounding the needle is drawn along the outside the needle thereby wiping the same. Preferably the web or membrane is composed of a resilient material and tends to contract around the needle by virtue of its resilient nature. Suitable materials for the membrane or web include elastomers such as silicones or silicone-based materials.
The sheath may have a pointed end to facilitate penetration into a vessel, e.g. via a rubber seal or cap provided on the vessel.
The sheath may have at least one aperture through its wall above the pointed end and/or it may have an aperture at its pointed end.
The sheath may be protected before use by a removable guard which is conveniently in the form of a part cylindrical wall.
The guard may be integral with the sheath and removable at one or more frangible connections.
The sheath may be removably attachable to the syringe through a push-on/pull-off friction fit or snap fit or through a threaded connection or a bayonet-type connection.
The sheath may be formed from a metal or a plastics material.